EP0639445A2 - Verfahren zum Trennen eines aus mehreren Komponenten bestehenden Stoffgemisches in einem Extruder - Google Patents

Verfahren zum Trennen eines aus mehreren Komponenten bestehenden Stoffgemisches in einem Extruder Download PDF

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Publication number
EP0639445A2
EP0639445A2 EP94111851A EP94111851A EP0639445A2 EP 0639445 A2 EP0639445 A2 EP 0639445A2 EP 94111851 A EP94111851 A EP 94111851A EP 94111851 A EP94111851 A EP 94111851A EP 0639445 A2 EP0639445 A2 EP 0639445A2
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EP
European Patent Office
Prior art keywords
pressure
low
pressure zone
zone
separation medium
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP94111851A
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German (de)
English (en)
French (fr)
Other versions
EP0639445A3 (enrdf_load_stackoverflow
Inventor
Hedi Dr.Rer.Nat. Ben-Nasr
Manfred Grabow
Klaus Reimann
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Fried Krupp AG Hoesch Krupp
Original Assignee
Fried Krupp AG Hoesch Krupp
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Publication date
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Publication of EP0639445A2 publication Critical patent/EP0639445A2/de
Publication of EP0639445A3 publication Critical patent/EP0639445A3/xx
Withdrawn legal-status Critical Current

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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G69/00—Macromolecular compounds obtained by reactions forming a carboxylic amide link in the main chain of the macromolecule
    • C08G69/02—Polyamides derived from amino-carboxylic acids or from polyamines and polycarboxylic acids
    • C08G69/08—Polyamides derived from amino-carboxylic acids or from polyamines and polycarboxylic acids derived from amino-carboxylic acids
    • C08G69/14—Lactams
    • C08G69/16—Preparatory processes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29B—PREPARATION OR PRETREATMENT OF THE MATERIAL TO BE SHAPED; MAKING GRANULES OR PREFORMS; RECOVERY OF PLASTICS OR OTHER CONSTITUENTS OF WASTE MATERIAL CONTAINING PLASTICS
    • B29B7/00—Mixing; Kneading
    • B29B7/80—Component parts, details or accessories; Auxiliary operations
    • B29B7/84—Venting or degassing ; Removing liquids, e.g. by evaporating components
    • B29B7/845—Venting, degassing or removing evaporated components in devices with rotary stirrers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29B—PREPARATION OR PRETREATMENT OF THE MATERIAL TO BE SHAPED; MAKING GRANULES OR PREFORMS; RECOVERY OF PLASTICS OR OTHER CONSTITUENTS OF WASTE MATERIAL CONTAINING PLASTICS
    • B29B7/00—Mixing; Kneading
    • B29B7/80—Component parts, details or accessories; Auxiliary operations
    • B29B7/86—Component parts, details or accessories; Auxiliary operations for working at sub- or superatmospheric pressure
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/25—Component parts, details or accessories; Auxiliary operations
    • B29C48/36—Means for plasticising or homogenising the moulding material or forcing it through the nozzle or die
    • B29C48/50—Details of extruders
    • B29C48/76—Venting, drying means; Degassing means
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/03—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor characterised by the shape of the extruded material at extrusion
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/25—Component parts, details or accessories; Auxiliary operations
    • B29C48/36—Means for plasticising or homogenising the moulding material or forcing it through the nozzle or die
    • B29C48/50—Details of extruders
    • B29C48/76—Venting, drying means; Degassing means
    • B29C48/762—Vapour stripping
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
    • B29K2077/00—Use of PA, i.e. polyamides, e.g. polyesteramides or derivatives thereof, as moulding material
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
    • B29K2105/00—Condition, form or state of moulded material or of the material to be shaped
    • B29K2105/26—Scrap or recycled material

Definitions

  • the invention relates to a method for separating a mixture of substances consisting of several components, which contains thermoplastic polymers as the main component and low molecular weight compounds as secondary components to be separated, by thermovacuum treatment of a melt of the mixture of substances in an extruder with several high and low pressure zones, one in the last low pressure zone upstream high pressure zones under the inlet pressure (p e ) a separation medium in which the low molecular weight compound is at least partially soluble is introduced into the melt and at least partly from a low pressure zone adjacent to this high pressure zone, in which a residual pressure (p e ) lower than the inlet pressure ( p) prevails when the separation medium loaded with secondary components is removed and collected outside the extruder.
  • DE 39 32 793 A1 Such a method is known from DE 39 32 793 A1 for the treatment of a polyamide 6 melt with water vapor, it also being pointed out that when using saturated water vapor with an incorrect setting of the pressure distributions to be avoided in the extruder, the vapor is avoided can emerge from the extruder in the direction opposite to the melt movement.
  • the invention dealt with in DE 39 32 793 A1 relates to the repeated treatment of polycaproamide melts and their copolymers in the extruder with superheated steam and thermovacuum degassing for the separation of low molecular weight compounds.
  • this atmospheric outlet is the lower limit for one by US Pat. No. 3,683,511 known alien DC method, in which residual pressures of up to 10 bar are provided in order to drive off volatile hydrocarbons from elastomers.
  • DE 39 32 793 A1 also deals with other processes for the thermovacuum treatment of polymer melts in an extruder, such as the introduction of saturated water vapor, as already mentioned.
  • the invention is based on the object of further developing the known continuous process and of creating an operationally reliable and economical process for the separation of low molecular weight compounds from polymer melts, in particular for the lactamization of polyamide-6, which, with relatively little energy expenditure, leads to low residual contents of low molecular weight compounds, thus leads to extensive cleaning of the polymer melt.
  • the starting material is a thermoplastic polymer in solid form (granules, chips, powder %), in the molten state, e.g. from a polyaddition reactor, or in the form of a polymer solution or polymer paste, and which can be carried out with further processing steps, such as admixing additives, granulating or subsequent processing, e.g. to spin fibers, can be advantageously combined.
  • the melt on its way through the extruder, first passes through a low pressure zone with a residual pressure (p) that meets the condition 1 bar ⁇ p ⁇ p c (where p c is the critical pressure of the separation medium) is sufficient, and is removed from the separation medium loaded with secondary components before the thermovacuum treatment of the melt by vacuum degassing at a vacuum (p u ) ⁇ 0.5 bar, preferably ⁇ 0.05 bar in the last low pressure zone.
  • thermovacuum treatment is therefore largely independent of the original amount of low-molecular compounds in the mixture of substances and regardless of whether a relatively, but also absolutely large or very large amount of release agent was previously introduced and discharged again at ⁇ 1 bar.
  • the thermal vacuum treatment practically limited to a final degassing, is particularly effective.
  • a basic process variant is preferred, in which the predominant part of the separation medium introduced into a high-pressure zone and loaded there with secondary components is directed countercurrently and is removed from the low-pressure extraction zone upstream of this high-pressure zone.
  • thermovacuum treatment should only be carried out after the content of low-molecular compounds has been reduced to ⁇ 10% of the starting content of the mixture of low-molecular compounds.
  • the separation medium should be introduced under a pressure p e which is above the residual pressure p of the associated low-pressure extraction zone, but should not exceed the critical pressure p c of the separation medium.
  • a residual pressure (p) between 1 and 8 bar and the introduction of the separation medium under a pressure (p e ), which is determined by the function p ⁇ p e ⁇ p c, are considered to be advantageous process parameters, predominantly for the zone with predominant reverse flow of the loaded separation medium given range. This is also the surprising finding that excellent cleaning effects can be achieved with relatively low differential pressures.
  • the separation treatment of the mixture of substances is carried out by a process in which the melt passes through two high-pressure zones, in which separation medium is introduced under pressure, in such a way that both high-pressure zones are assigned to the zone region with reverse flow such that a low-pressure zone in front of both high-pressure zones in which the defined residual pressure (p) prevails, and that loaded release agent is derived from both low-pressure zones.
  • the separation medium can be water or other media, such as alcohols, that are liquid under normal conditions (1 bar absolute and 20 ° C).
  • gaseous CO2 or N2 is used as the separation medium, which is introduced into the melt as compressed gas.
  • the gas is (in the thermodynamic sense) solvent for the low-molecular compound, so that even when using such gases, one can speak of a kind of solvent extraction, a selective removal of certain substances.
  • liquid release agent or solvent and from CO2 or N2 is used.
  • the liquid solvent (under normal conditions) can also be introduced in vapor form.
  • a higher solvency of compressed gases can be used in favor of a better cleaning effect.
  • the advantages of the invention therefore come into play in principle in the treatment of substance mixtures which contain thermoplastic polymers as the main component, the secondary components also being able to be referred to as impurities or by-products of a process.
  • impurities are, for example, solvent residues, for example from the polymerization process, monomers, oligomers, catalyst residues, by-products, for example from the polyreaction, degradation products or other substances such as odors and / or flavorings, additives or foreign substances which have diffused in during use and which have the properties of Affect polymers and / or restrict their use.
  • Secondary components in the sense of this invention can also be valuable materials that are recovered.
  • the extracted ⁇ -caprolactam is recovered and can be used after preparation for the production of polyamide-6 (polycaprolactam).
  • Raw plastic and / or the recyclate can be a mixture with the main component polyamide-6 and the secondary component ⁇ -caprolactam.
  • the process with water as the separation medium, which is introduced into the melt as water vapor, is operated with the proviso that at least 200% of water, based on the initial mass content of the mixture of low-molecular compounds, such as ⁇ -caprolactam, are introduced.
  • more than 50% by mass of the water is introduced into the first high-pressure zone and less than 50% by mass into the second high-pressure zone closer to the final thermovacuum treatment be, and it is provided that the residual pressure (p1) in the low pressure zone upstream of the first high pressure zone is higher than the residual pressure (p2) in the second low pressure zone, and that the difference (p2 - p1) of the residual pressures is at least 1 bar.
  • Polyamide 6 is obtained on an industrial scale from ⁇ -caprolactam, predominantly by hydrolytic polymerization. This results in a thermodynamic equilibrium between the polycondensate polyamide-6 (PA 6), the monomer ⁇ -caprolactam and various, predominantly cyclic dimers and oligomers, which essentially depends on the temperature and water content. This mixture with about 8 to 10% monomer content ( ⁇ -caprolactam) must be demonomerized to the lowest possible caprolactam content. To this end, two methods are alternatively practiced regularly, namely vacuum degassing of the volatile constituents from the polymer melt (e.g. US 3,578,640) or extraction of the low molecular weight compounds from PA 6 granules with hot water under slight excess pressure.
  • vacuum degassing of the volatile constituents from the polymer melt e.g. US 3,578,640
  • extraction of the low molecular weight compounds from PA 6 granules with hot water under slight excess pressure e.g. US 3,578,640
  • both methods are not only time-consuming and cost-intensive, but also sometimes have considerable technical and / or environmental problems.
  • the moist granules (approx. 30% by weight of water) have to be dried with high energy input (residual moisture content approx. 0.1%). Remelting of the granules is also necessary for mixing additives and / or for further processing. In addition to the additional energy expenditure, the back reaction to monomers and oligomers must also be accepted.
  • a better or at least a comparable degree of cleaning can be achieved with the method according to the invention with considerably less time and cost than with the prior art.
  • a crude polyamide-6 which contains 8 to 10% by weight ⁇ -caprolactam
  • the caprolactam is extracted from the polymer melt with water vapor at a pressure which is above atmospheric pressure, preferably with counterflow of the separating medium, and is removed from the extruder together with the water vapor and small amounts of further extractable constituents.
  • the water vapor is liquefied by relaxing to normal pressure and cooling.
  • the caprolactam always remains dissolved in the aqueous phase and does not lead to constipation Pipelines.
  • the recovery of caprolactam is also much more economical here, since it is obtained in concentrated form due to the smaller amounts of water and, due to the very short extraction time in the extruder, almost only caprolactam enters the extract phase.
  • the water due to the increased pressure, the water partially dissolves in the polymer melt, which results in better diffusion and a higher mass transfer rate.
  • the water vapor loaded with the extracted substances is extracted from the extruder under pressure.
  • considerably more water can be used and the flow rate of the vapor phase in the extruder can nevertheless be kept lower.
  • the extraction pressure in the extruder cannot be increased arbitrarily, because at high pressures, in particular ⁇ the critical pressure (of the solvent), the solubility of the solvent in the polymer melt increases very greatly and has an adverse effect on the process control.
  • pressures between 1 bar abs. and about 20 bar abs. proven to be cheap.
  • a co-rotating twin-screw kneader is particularly suitable as an extruder, which is based on the modular principle and thus has a high degree of flexibility.
  • FIG. 1 shows an extruder 1 with a feed hopper 2, a feed zone 3, which is usually cooled, and a plasticizing zone 4 for melting the mixture of substances.
  • the plasticizing zone 4 is followed by a low-pressure zone 5, which merges via an extraction zone 6 into a high-pressure zone 7, to which a throttle device 8 is assigned.
  • the throttle device 8 is followed by a last low-pressure zone 9 and at the end a last high-pressure zone 10, which is assigned to the extruder head 11.
  • the structure of the extruder 1, namely its screw housing in a modular system, is indicated by lines 12.
  • the pressure distribution in the extruder itself is essentially determined by the geometry of the screw or the screws.
  • the high-pressure zone 7 has an inlet connection 18, into which a water vapor delivery line 19 opens.
  • a double arrow 20 is intended to illustrate the adjustability of the throttle element 8.
  • the last low-pressure zone 9 has a degassing opening 21 which is connected to a vacuum system, not shown.
  • An arrow symbol 22 indicates the vacuum degassing.
  • the mixture of substances symbolized by an arrow 23, is fed to the feed hopper 2, and the cleaned main component 24 emerges from the extruder head 11.
  • the mixture 1, namely the thermoplastic polymer is fed to the extruder 1.
  • the feed zone 3 which is usually cooled, is followed by the melting of the substance mixture in the plasticizing zone 4.
  • the extraction zone 6 the secondary components or impurities are extracted from the polymer melt using a solvent, for example water.
  • a solvent for example water.
  • water vapor from the water vapor delivery line 19 is fed to the extruder in the high-pressure zone 7 via the inlet connection 18.
  • the solvent flows towards the polymer melt, picks up the impurities to be removed and is removed from the extruder from the low-pressure zone 5, via line 14, the control valve 15, with which the residual pressure can be determined, and the heat exchanger 16.
  • the ratio of amount of release agent - here water - to the polymer to be cleaned is 1:20 to 1: 2, preferably 1:10 to 1: 5.
  • the control valve 15 is used to set and maintain a residual pressure (p) corresponding to the function p c ⁇ p ⁇ 1 bar absolute.
  • the possibly still vaporous mixture of separating (solvent) and extracted low molecular weight compounds is liquefied and cooled.
  • This mixture is drawn off via outlet 17 and processed in a further process step, the extracted substances, for example ⁇ -caprolactam in polyamide-6, being recovered and the regenerated release agent being able to be fed back to the extruder if necessary.
  • a melt seal is created by jamming the polymer melt. This can take place either by means of a suitable screw construction or selection of suitable screw elements or, as here, by means of an expediently adjustable throttle device 8.
  • thermovacuum treatment is finally carried out, with the release agent absorbed by the polymer melt, here water and largely the remaining residual low-molecular-weight compounds, being removed by applying a vacuum.
  • the release agent absorbed by the polymer melt, here water and largely the remaining residual low-molecular-weight compounds, being removed by applying a vacuum.
  • a better final degassing is achieved than according to the prior art, because the polymer melt in the extraction zone 6, which is under an increased pressure, loads to a greater extent with the solvent and this is released in the last low-pressure zone 9 and for controlled foaming the polymer melt leads.
  • the cleaned polymer melt 24 leaves the extruder 1 via the extruder head 11 and is either granulated or fed directly to a subsequent processing process, for example a second processing extruder or a spinning device.
  • the extruder 1 according to FIG. 2 has a second low pressure zone 25 and a second high pressure zone 26 between the first high pressure zone 7 and the last low pressure zone 9.
  • the latter is assigned a further inlet connection 32 and a pressure delivery line 33, while the second low-pressure zone 25 has a further one Exhaust port 27 has. From this, a delivery line 28 leads via a further control valve 29 to a further heat exchanger 30 with the associated outlet 31.
  • FIG. 2 illustrates a further embodiment variant of the invention, which is particularly suitable for the extraction of larger amounts of impurities from the polymer melt and / or for achieving deep cleaning.
  • polyamide-6 which is taken from a polycondensation reactor and contains 8 to 10% by weight of ⁇ -caprolactam, can advantageously be used largely according to this variant, i.e. demonomerized to below 1000 ppm ⁇ -caprolactam. Water is again used as the release agent.
  • the first melt seal is in turn built up between the plasticizing zone 4 and the first low-pressure zone 5.
  • Part of the water is added to the extruder in the high-pressure zone 7 via the water vapor feed line 19, flows in the opposite direction, is loaded with secondary components and is finally discharged from the first low-pressure zone 5.
  • the first extraction zone 6 is followed by a second extraction zone, which largely coincides with the second low-pressure zone 26 and partly with the second high-pressure zone.
  • the second high-pressure zone is of course delimited from the subsequent last low-pressure zone 9 melt seal.
  • Another part of the water is fed to the extruder in the second high-pressure zone 26 via the further steam delivery line 33.
  • the remaining secondary components are extracted and removed with the steam and fed to the own further heat exchanger 30.
  • the melt seal between the extraction zone 6 and the second low-pressure zone 25 can also advantageously be designed so that the release agent which is in the extruder is added to the first high-pressure zone 7, partly also flows in the flow direction of the polymer melt, so that a countercurrent as well as a cocurrent extraction takes place.
  • the ratio of the amounts of release agent for countercurrent and cocurrent extraction can be varied between 1: 1 and 20: 1.
  • the release agent or amount of water for the second extraction zone is generally smaller than the amount of extractant for the first extraction zone 6, a ratio of 1: 2 to 1:10 having proven particularly favorable.
  • the ratio of the total amount of release agent to the polymer to be cleaned is 1:10 to 1: 1, preferably 1:10 to 1: 2.
  • the cleaning process according to the invention for thermoplastic polymers was explained here with reference to FIGS. 1 and 2, where only one extruder is used. However, it is also within the meaning of this invention to use, for example, two extruders connected in series and to combine the extraction process with a further, for example a subsequent processing step.
  • the separation process can also be carried out in several stages, different process pressures being set in the individual extraction zones and / or different solvents, for example water and CO2 or N2, being used.
  • the use of two extruders also offers the advantageous possibility of adapting the screw speed to the changing consistency of the polymer melt.
  • the method according to the invention can also advantageously be connected to an upstream process, for example a manufacturing process for raw plastics or a conventional sorting and / or cleaning process for recycled plastics.
  • 3 to 5 show the pressure profile in extruders during the operation of the method according to the invention.
  • the introduction of the separation medium is symbolized by the introduction arrows 34 and 36, the discharge of the loaded separation medium by the discharge arrows 35 and 37.
  • the pressure p d1 is built up in the first melt seal , thus creating a first high-pressure zone H1.
  • the second and third melt seals generate the pressures p d2 and P d3 for the second high pressure zone H2 and the third high pressure zone H3.
  • the position of the supply arrow 34 illustrates that the separation medium in the rising branch of the first low-pressure zone N1 is supplied at an introductory pressure P e1 and, following the slightest resistance, seeks its way backwards and is largely discharged again when the residual pressure p 1 is loaded, for which the discharge arrow 35 stands.
  • the inlet pressure p e2 is significantly lower than the inlet pressure p e1 and the residual pressure p2 in the second low-pressure zone N2 is set lower than before and is only slightly above 1 bar.
  • the final vacuum degassing 22 takes place in the third low-pressure zone N3 at an underpressure p v which is clearly below 0.5 bar.
  • the separating medium is essentially discharged backwards, but smaller quantities of separating agent are taken from the low pressure zone N1, overcoming the corresponding melt seal, into the following second low pressure zone. This also applies to the transport of the melt from the second low pressure zone N2 to N3.
  • FIG. 4 shows the process variant in which the second low-pressure zone N2 (as in FIG. 1) has a counterflow of the separation medium is set, while in the first low pressure zone N2 melt and release agent flow in one direction.
  • examples 1 and 2 are not the subject of this invention. They are only intended to illustrate the advantages of the method according to the invention compared to the prior art.
  • a polyamide 6 recyclate (regranulate) with an ⁇ -caprolactam content of 6,400 mg / kg is treated in a co-rotating twin-screw kneader, type ZSK 40, according to FIG. 2, the low-pressure zones 5 and 25 being operated as thermovacuum treatment zones with vacuum degassing . Release agents or entraining agents are not added.
  • the polymer melt thus purified is then strand-granulated and analyzed for ⁇ -caprolactam.
  • Example 2 The same starting material as in Example 1 is degassed using water as entrainer, but otherwise with comparable process parameters as in Example 1. Via the steam delivery lines 19 and 33 are each 0.85 kg / h water in the plastic melt. The vacuum is 9 mbar above the first low pressure zone 5 and 8 mbar above the second and the last low pressure zone 25 and 9. The ⁇ -caprolactam content is reduced to 770 mg / kg, corresponding to a degree of lactamization of 88%. Due to the already mentioned tendency of ⁇ -caprolactam to settle on the walls of the lines to the evacuation system, trouble-free operation can only be guaranteed here with great effort.
  • a polyamide 6 recyclate (regranulate) with an ⁇ -caprolactam content of 6,400 mg / kg is cleaned in a co-rotating twin-screw kneader, type ZSK 40, according to FIG. 1 by solvent extraction.
  • a throughput of 20 kg / h 19 4 kg / h of water are fed to the extruder in the high-pressure zone 7 at a pressure of 12 bar absolute via the steam delivery line.
  • the throttle device 8 With the help of the throttle device 8, a melt seal is built up, so that the added water flows largely against the polymer melt, thereby becoming increasingly loaded with the contaminants to be extracted and being absolutely removed from the extruder from the low-pressure zone 5 at a pressure of 4 bar.
  • a small part of the added water is absorbed by the polymer melt and removed with the remaining impurities in the last low-pressure zone 9 under a vacuum of 1 mbar.
  • the cleaned polymer melt 24 is then strand-granulated and analyzed for ⁇ -caprolactam.
  • the ⁇ -caprolactam content is reduced to 330 mg / kg, corresponding to a degree of lactamization of 95%.
  • a polyamide 6 recyclate (regranulate) with an ⁇ -caprolactam content of 6,400 mg / kg is in a co-rotating twin-screw kneader, Type ZSK 40, cleaned according to FIG. 1 by solvent extraction.
  • a crude polyamide-6 with a ⁇ -caprolactam content of 9.3% by weight is cleaned in a co-rotating twin-screw kneader, type ZSK 40, according to FIG. 2 by solvent extraction with water.
  • 19 8 kg / h of water vapor are fed to the extruder at a pressure of 4 bar absolute and largely discharged from the first low-pressure zone 5 at a pressure of 3 bar via the water vapor delivery line.
  • the first extraction is followed by a second extraction.
  • the extracted caprolactam always remains dissolved in the aqueous phase and does not lead to the blockage of pipelines. This ensures a trouble-free, reliable continuous driving style.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Mechanical Engineering (AREA)
  • Medicinal Chemistry (AREA)
  • Polymers & Plastics (AREA)
  • Organic Chemistry (AREA)
  • Health & Medical Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Polyamides (AREA)
  • Processing And Handling Of Plastics And Other Materials For Molding In General (AREA)
  • Extraction Or Liquid Replacement (AREA)
  • Extrusion Moulding Of Plastics Or The Like (AREA)
  • Separation, Recovery Or Treatment Of Waste Materials Containing Plastics (AREA)
EP94111851A 1993-08-20 1994-07-29 Verfahren zum Trennen eines aus mehreren Komponenten bestehenden Stoffgemisches in einem Extruder Withdrawn EP0639445A2 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE4328013A DE4328013C1 (de) 1993-08-20 1993-08-20 Verfahren zum Trennen eines aus mehreren Komponenten bestehenden Stoffgemisches in einem Extruder
DE4328013 1993-08-20

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Publication Number Publication Date
EP0639445A2 true EP0639445A2 (de) 1995-02-22
EP0639445A3 EP0639445A3 (enrdf_load_stackoverflow) 1995-03-29

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EP94111851A Withdrawn EP0639445A2 (de) 1993-08-20 1994-07-29 Verfahren zum Trennen eines aus mehreren Komponenten bestehenden Stoffgemisches in einem Extruder

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US (1) US5459168A (enrdf_load_stackoverflow)
EP (1) EP0639445A2 (enrdf_load_stackoverflow)
JP (1) JPH07149816A (enrdf_load_stackoverflow)
DE (1) DE4328013C1 (enrdf_load_stackoverflow)

Cited By (1)

* Cited by examiner, † Cited by third party
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DE102010003196A1 (de) * 2010-03-24 2011-09-29 Voith Patent Gmbh Verfahren zum Reinigen von wiederaufzubereitenden Papiermaschinenbespannungen

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